Testing switches in a power converter

ABSTRACT

A switching network includes a switch, a driver for the switch, and a floating-regulator that powers the driver. The floating-regulator includes a shunt that is used only when testing the network. The shunt diverts biasing current so that it does not interfere with a measurement of an electrical property of a switch.

FIELD OF INVENTION

This invention relates to testing of an integrated circuit, and inparticular, to testing switches for a switched-capacitor circuit.

BACKGROUND

A power converter often includes a switched-capacitor circuit thatconverts one voltage into another voltage. The switched-capacitorcircuit generally includes a switching network having one or moreswitches that are used to interconnect various capacitors. When theseswitches are closed, they handle significant amounts of current.

The switches are typically implemented as field-effect transistors. Avoltage that is applied to a gate terminal of the transistor closes thisswitch. This voltage controls the existence of a conducting channelbetween the transistor's source and drain terminals. Like any conductingchannel, this channel will have some resistance to current flow. Becausethis channel is between the transistor's drain and source, and becauseit is established in the transistor's “ON” state, this resistance isoften called the “RDSON” of the transistor.

The value of RDSON is of great significance. This is particularly sowhen the switch is called upon to handle significant amounts of current.It is therefore important that the channel's resistance conform to thedesign specification.

Another parameter of interest is the transistor's leakage current. Evenwhen no conducting channel connects the source and drain across thegate, it is still possible for a few charge carriers to diffuse from thesource all the way to the drain. This results in a small leakagecurrent.

Both the transistor's RDSON and its leakage current are subject tovariability as a result of imperfections in the manufacturing process.Thus, it is important to measure both RDSON and leakage current as apart of the manufacturing process. Doing so provides the opportunity toreject defective switches and to thereby avoid the likelihood of placinga faulty power converter into the stream of commerce.

SUMMARY

In one aspect, the invention features an apparatus that includes aswitching network. The switching network includes switches, drivers forthose switches, and floating-regulators that power the drivers. Eachfloating-regulator includes a shunt that is used only when testing thenetwork. The shunt diverts biasing current so that it does not interferewith a measurement of an electrical property of a switch.

In another aspect, the invention features a switching network that, whenconnected to capacitors, forms a switched-capacitor network fortransforming a first voltage into a second voltage. The switchingnetwork includes a plurality of switches, a corresponding plurality ofdrivers, and a corresponding plurality of floating-regulators. Amongthese are first and second switches, a first driver, and a firstfloating-regulator that has first and second current paths, togetherwith a shunt for selecting between them. Current that proceeds along thefirst current path is provided to a second floating-regulator to providepower for driving the second switch. However, current that proceedsalong the second path is diverted. As a result, this current fails toprovide power for driving any switch.

Some embodiments include a controller that causes the shunt to selectthe second path.

In other embodiments, during operation, the switching network comprisesa node of lower electrical potential. This node has an electricalpotential that is lower than all other electric potentials in theswitching network. In such embodiments, the second path leads to thisnode of lower electrical potential. In other embodiments, this node oflower electrical potential is the node of lowest electrical potential.

Yet other embodiments include a controller configured to determinewhether a switch in the switching network has an electrical parameterthat complies with a design specification. Such a controller causes abias current in the switch and diverts the bias current so that itavoids interfering with measurement of the electrical parameter. Such acontroller also applies an electrical stimulus, measures an electricalresponse, derives the electrical parameter from the electrical response,and determines that the electrical parameter falls outside of the designspecification and identifies the switching network as being defective.

Also among the embodiments are those that include a controllerconfigured to measure an extent to which a switch conducts electriccurrent when the switch is held in a conducting state. Such a controllercauses a bias current to hold the switch in the conducting state,diverts the bias current so that the bias current avoids interferingwith a known current that is injected through the switch, causesinjection of the known current through the switch, measures a voltageacross the switch, and determines the extent to which the switchconducts based on the measurement of the voltage and the known current.

Yet other embodiments include a controller configured to determinewhether a switch in the switching network has an electrical parameterthat complies with a design specification. In such embodiments, thecontroller causes a bias current in the switch, diverts the bias currentso that the bias current avoids interfering with measurement of theelectrical parameter, measures the electrical parameter, determines thatthe electrical parameter falls outside of the design specification, andidentifies the switching network as being defective.

Still other embodiments include a controller configured to determine aleakage current of a switch in the switching network. Such a controllercauses a bias current to bias the switch to be in a non-conducting stateand diverts the bias current so that the bias current avoids interferingwith measurement of the leakage current.

Other embodiments include a power converter. In these embodiments, theswitching network and capacitors define a switched-capacitor networkthat is a constituent element of the power converter. Among theseembodiments are those that also include a controller that controls theswitches. Also among these embodiments are those in which the shuntnever switches between the first and second paths.

In other embodiments, the plurality of switches comprises a first set ofswitches that are arranged in series to define a first charge-transferpath that extends from the switching network's input to its output. Thisfirst charge-transfer path comprises nodes at which switches from thefirst set of switches connect. These nodes are also configured to beconnected to the capacitors.

In other embodiments, the plurality of switches comprises first andsecond sets of switches. Switches from the first set are arranged inseries to define a first charge-transfer path and switches from thesecond set are likewise arranged in series to define a secondcharge-transfer path. Both charge-transfer paths extend from theswitching network's input to its output. The first charge-transfer pathcomprises nodes at which switches from the first set of switches connectto each other. These nodes are configured to be connected to a firstplurality of capacitors. Meanwhile, the second charge-transfer pathcomprises nodes at which switches from the second set of switchesconnect to each other. These nodes are configured to be connected to asecond plurality of capacitors.

Some embodiments also include a monolithic substrate into which theswitching circuit is integrated.

Alternative embodiments have first and second monolithic substrates. Inthese embodiments, the switching circuit is integrated into the firstmonolithic substrate and the capacitors are integrated into the secondmonolithic substrate. The first and second monolithic substrates areinterconnected so that the switching circuit is electrically connectedto the capacitors.

Some embodiments include a monolithic substrate and a plurality ofcapacitors. In these embodiments, the switching circuit is integratedinto the monolithic substrate and the capacitors are connected to theswitching circuit.

Other embodiments include those in which the switches comprise powerFETs.

In yet other embodiments, each switch has multiple parallel pathsbetween its drain and its source, with each such path being individuallycontrolled.

Additional embodiments include those in which the switches aredistributed between first and second charge-transfer paths that bothextend between an input and an output of the switching network. In theseembodiments, the floating-regulators are cross-coupled between the firstand second charge-transfer paths.

Still other embodiments are those in which the first floating-regulatorcomprises a regulator switch to regulate flow of charge into the firstdriver and a Zener diode that causes the flow of charge to be providedat a fixed offset from a floating voltage.

Additional embodiments include those in which the floating-regulatorcomprises a regulator switch to regulate flow of charge into the firstdriver and conducting paths for supplying currents to the regulatorswitch. These conducting paths extend between different sources ofcharge and the regulator switch.

Also among the embodiments are those in which the firstfloating-regulator comprises a regulator switch and diodes that connectthe regulator switch to corresponding sources of electric charge.

In another embodiment, the first floating-regulator includes a regulatorswitch to regulate flow of charge into the first driver and a Zenerdiode. The Zener diode causes the flow of charge to be provided at afixed offset from a floating voltage.

Also among the embodiments are those in which the firstfloating-regulator includes a regulator switch to regulate flow ofcharge into the first driver and a plurality of conducting paths forsupplying currents to the regulator switch. These the conducting pathsextend between different sources of charge and the regulator switch.Examples of different sources of charge include different capacitors towhich the switching network is connected and also an external powersupply that is outside the switched-capacitor network altogether.

In some embodiments, the first floating-regulator includes a regulatorswitch and first and second diodes. The diodes connect the regulatorswitch to different sources of charge.

In yet other embodiments, the first floating-regulator includes a devicethat permits to current flow unless the potential imposed across itsterminals is of a first polarity and has a magnitude less than athreshold. Such embodiments feature a regulator switch that regulatescurrent into a first driver and also into the device.

In another aspect, the invention features a method comprising testing anelectrical parameter of a switch in a switching network in an integratedcircuit, that, when connected to capacitors, forms a switched-capacitornetwork for transforming a first voltage into a second voltage, theswitching network having a plurality of switches, a correspondingplurality of drivers, and a corresponding plurality offloating-regulators. In such a method, testing the electrical parametercomprises causing a first current, at least some of which will be usedto bias the switch, diverting the current along a path such that thecurrent avoids interference with a measurement, and carrying out themeasurement.

In some practices, the method includes, after having diverted thecurrent, measuring a leakage current of the switch.

In other practices, the method includes, measuring an RDSON of theswitch.

Other practices further include providing a stimulus to the switch,measuring a response to the stimulus, and based on the response,determining the electrical parameter.

In another aspect, the invention includes testing a leakage current of afirst switch in a switching network in an integrated circuit, that, whenconnected to capacitors, forms a switched-capacitor network fortransforming a first voltage into a second voltage. The switchingnetwork includes a plurality of switches, one of which is the firstswitch. It also includes a corresponding plurality of drivers, and acorresponding plurality of floating-regulators. Testing the leakagecurrent includes causing a first current, at least some of which will beused to bias the first switch, diverting it along a path such that itavoids interference with a measurement of a second current, measuringthe second current, and determining the leakage current at least in partbased on the measurement of the second current.

In some practices, the method comprises connecting an external voltagesource across the switch. Such an external voltage source is external tothe switched-capacitor network. As such, it excludes the capacitors ofthe switched-capacitor network itself. The second current is currentthat enters the switching network.

Additional practices include suppressing the ability of the secondcurrent from flowing along a path other than a charge-transfer path thatleads to the first switch.

In those practices in which the first switch is in series with a secondswitch on the charge-transfer path, the method also includes suppressingthe current that enters the switching network from flowing along thecharge-transfer path towards the second switch.

In yet other practices, one of the floating-regulators controls drivingof the first switch. Among these practices are those in which the firstcurrent is one that flows through this floating-regulator.

Further practices are those in which the first current carries power andwherein diverting the first current includes wasting this power.

In those cases in which the switches are in series along acharge-transfer path, there exists practices of the invention in whichdiverting the first current includes causing the first current to avoidflowing along the charge-transfer path.

In another aspect, the invention features an apparatus comprising aswitching network. The switching network, when connected to capacitors,forms a switched-capacitor network for transforming a first voltage intoa second voltage. The switching network includes a plurality ofswitches, a corresponding plurality of drivers, and a correspondingplurality of floating-regulators. Among the switches is a first switchthat connects to a floating voltage. Among the drivers is a first driverto drive the first switch using a drive voltage. A firstfloating-regulator from among the regulators relies on voltage providedby an external voltage source for causing the drive voltage to be at afixed offset from the floating voltage. This external voltage source isone that is external to the switched-capacitor circuit. As such, it isnot one of the capacitors that forms the switched-capacitor network.

In some embodiments, the first floating-regulator includes a firstoutput and a second output. The first output is maintained at a voltagethat depends on the floating voltage; the second output is maintained ata voltage that depends on the offset. In such embodiments, first driveris connected between the first and second outputs.

Also among the embodiments are those in which first floating-regulatorincludes a first path that connects a voltage provided by the externalvoltage source to the first driver and a second path that connects avoltage corresponding to the offset to the first driver. In some ofthese embodiments, the first path includes a regulator switch and thesecond path includes a Zener diode.

In some aspects, the invention features determining RDSON values foreach switch from a plurality of switches that, together with a pluralityof drivers that drives the switches and a plurality offloating-regulators for controlling the drivers, forms a switchingnetwork. The switching network, when connected to capacitors, forms aswitched-capacitor network for transforming a first voltage into asecond voltage. The switches are disposed in series along acharge-transfer path. Among the switches are first and second switchesthat connect to corresponding first and second floating voltages.Determining RDSON values comprises causing a known current to flowthrough the charge-transfer path and concurrently determining RDSONvalues for each of the first and second switches.

Some practices of the method include measuring a first voltage acrossthe first switch, measuring a second voltage across the second switch,and based on the first and second voltages, determining RDSON values forthe first and second switches.

Also among the practices of the invention are those in which causing aknown current to flow through the charge-transfer path includesinhibiting opportunities for the current to stray from thecharge-transfer path.

In another aspect, the invention features a switching network that, whenit is connected to capacitors, forms a switched-capacitor network fortransforming a first voltage into a second voltage. The switchingnetwork includes a floating-regulator that has two terminals. Oneterminal receives charge from one of the capacitors and the otherterminal receives charge from another one of the capacitors. Thefloating-regulator uses charge from one of the two capacitors to cause adriver to drive a switch from the switched-capacitor network such that adriving voltage for the switch is equal to a fixed offset from afloating voltage that is present on one of the switch's terminals.

In another aspect, the invention includes a switching network that, whenconnected to capacitors, forms a switched-capacitor network fortransforming a first voltage into a second voltage. Such a switchingnetwork includes a switch, a driver, and a floating-regulator. Thefloating-regulator includes a first current path and a second currentpath. Current that proceeds along the first current path drives theswitch; current that proceeds along the second path is diverted suchthat it fails to provide power for driving any switch. Thefloating-regulator includes a shunt for causing the current to proceedalong one of the first and second paths.

Some embodiments include a controller. In some of these embodiments, thecontroller causes the shunt to select the second path. In others, thecontroller determines whether a switch in the switching network has aleakage current that complies with a design specification. In thesecases, the controller causes a bias current in the switch, causes adiversion of this bias current so that the bias current avoidsinterfering with measurement of the leakage current, applies a voltageacross the switch, obtains a measurement of a current that flows inresponse to application of the voltage, derives the leakage current fromthe measurement, determines that the leakage current falls outside ofthe design specification, and identifies the switching network as beingdefective. In still others of these embodiments, the controllerestimates a switch's leakage current in part by causing a bias currentthat biases the switch to be in a non-conducting state and diverting thebias current so that it avoids interfering with measurement of theleakage current.

In other embodiments, the second path leads to a node of lowestelectrical potential. This node has an electrical potential that islower than all other electric potentials in the switching network.

Also among the embodiments are those that include a power converter.Among these embodiments are those in which the switching network and thecapacitors define a switched-capacitor network that is a constituent ofthe power converter. The power converter includes a controller forcontrolling the switching network.

Also among the embodiments that include a power converter are those inwhich the switching network and the capacitors define aswitched-capacitor network that is a constituent of the power converter.During operation of the power converter, the shunt never switchesbetween the first and second paths.

In some embodiments, the switching network includes first and secondsets of switches. The switches from the first set are arranged in seriesto define a first charge-transfer path that extends from the switchingnetwork's input to its output. Meanwhile, the switches from the secondset of switches are arranged in series to define a secondcharge-transfer path that also extends from between the input andoutput. The first charge-transfer path includes nodes at which switchesfrom the first set of switches connect to each other. These nodesconnect to a first set of capacitors. The second charge-transfer pathlikewise includes nodes at which switches from the second set ofswitches connect to each other. These nodes connect to a second set ofcapacitors.

Also among the embodiments are those in which the switching circuit isintegrated into a monolithic substrate.

It is not necessary to have only one such substrate. In otherembodiments, the switching circuit is integrated into a first monolithicsubstrate and the capacitors are integrated into a second monolithicsubstrate that is interconnected with the first monolithic substrate.

In other embodiments, the capacitors are not integrated into asubstrate. In these embodiments, the switching circuit is integratedinto the monolithic substrate and the capacitors are connected to theswitching circuit without having to be on a monolithic substrate.

Embodiments further include those in which the switch is a power FET andthose in which the switch is one of several switches that aredistributed between first and second charge-transfer paths. Both ofthese charge-transfer paths extend between an input and an output of theswitching network. In such embodiments, the floating-regulator iscross-coupled between the first and second charge-transfer paths.

Also among the embodiments are those in which the floating-regulatorincludes a regulator switch to regulate flow of charge into the driverand a Zener diode. The Zener diode causes the flow of charge to beprovided at a fixed offset from a floating voltage.

In yet other embodiments, the floating-regulator includes a regulatorswitch to regulate flow of charge into the driver and a plurality ofconducting paths for supplying currents to the regulator switch. Theseconducting paths extend between different sources of charge and theregulator switch.

Further embodiments include those in which the floating-regulatorincludes a first diode that connects the regulator switch to a firstsource of charge and a second diode that connects a regulator switch toa second source of charge.

In still other embodiments, at least some of current that proceeds alongthe first current path and that drives the switch is provided to anadditional floating-regulator to provide power for driving an additionalswitch.

In another aspect, the invention features a method that includesestimating a leakage current of a switch in a switching network in anintegrated circuit. The switching network, when connected to capacitors,forms a switched-capacitor network for transforming a first voltage intoa second voltage. It includes a driver and a floating-regulator.Estimating the leakage current includes causing a first current, atleast some of which will be used to bias the switch, diverting the firstcurrent along a path such that the first current avoids interferencewith a measurement of a second current, obtaining a measurement of thesecond current, and determining, the leakage current based at least inpart based on the measurement of the second current.

In some practices, the switch is one of a plurality of switches that arein series along a charge-transfer path. In these practices, divertingthe first current includes causing the first current to avoid flowingalong the charge-transfer path.

Alternative practices of the invention include connecting a voltagesource across the switch. The voltage source is one that is external tothe switched-capacitor network. This means that it is not one of thecapacitors in the switched-capacitor network. The second current iscurrent that enters the switching network.

Yet other practices of include suppressing the ability of the secondcurrent from flowing along a path other than a charge-transfer path thatleads to the switch.

In those cases in which the switch is a first switch that is in serieswith a second switch along a charge-transfer path, there are practicesof the method that also include suppressing the current that enters theswitching network from flowing along the charge-transfer path towardsthe second switch.

Additional practices include causing the first current to flow throughthe floating-regulator, which controls driving of the switch.

Also among the practices of the invention are those that include wastingpower by diverting the first current.

In another aspect, the invention features a switching network that, whenconnected to capacitors, forms a switched-capacitor network fortransforming a first voltage into a second voltage. The switchingnetwork includes a switch that connects to a floating voltage, a driverconfigured to drive the switch using a drive voltage, and afloating-regulator that relies on a voltage provided by voltage sourcefor causing the drive voltage to be at a fixed offset from the floatingvoltage. This voltage source is one that is external to theswitched-capacitor circuit. As such, it does not include a capacitorfrom the switched-capacitor circuit.

Among the embodiments are those in which the floating-regulator includesfirst and second outputs. The first output is maintained at a voltagethat depends on the floating voltage and the second output is maintainedat a voltage that depends on the offset. The driver is connected betweenthe first and second outputs.

Also among the embodiments are those in which the floating-regulatorincludes a first path that connects a voltage provided by the externalvoltage source to the driver and a second path that connects a voltagecorresponding to the offset to the driver.

In some embodiments, the floating-regulator includes a regulator switchdisposed along a first path and a Zener diode disposed along a secondpath. The first path connects to a voltage provided by a voltage sourcethat is external voltage to the driver and the second path connects to avoltage corresponding to the offset to the driver.

Other embodiments include a controller configured to cause a biascurrent to hold the switch in a conducting state and to divert the biascurrent so that it avoids interfering with a known current that isinjected through the switch. The controller also causes injection of theknown current through the switch, measures a voltage across the switch,and estimates an RDSON of the switch based on the measurement of thevoltage and the known current.

In still other embodiments, the switch is one of a plurality of switchesthat are arranged in series to define a first charge-transfer path thatextends from an input of the switching network to an output of theswitching network. The first charge-transfer path includes nodes atwhich switches from the first set of switches connect. These nodes areconfigured to be connected to the capacitors.

In another aspect, the invention includes estimating an RDSON value fora switch that, along with a driver that drives the switch and afloating-regulator for controlling the driver, is a constituent of aswitching network that when connected to capacitors, forms aswitched-capacitor network for transforming a first voltage into asecond voltage. The switch is disposed along a charge-transfer path andconnects to a floating voltage. Estimating RDSON values includes causinga known current to flow through the charge-transfer path and estimatingan RDSON value for the switch.

In some practices, the switch is one of a plurality of switches inseries along the charge-transfer path and the method includesconcurrently obtaining voltage measurements across each of the switchesand estimating the RDSON values based on the voltage measurements.

Other practices include causing a known current to flow through thecharge-transfer path includes inhibiting opportunities for the currentto stray from the charge-transfer path.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will be apparent from thefollowing description and the accompanying figures, in which:

FIG. 1 shows a power converter that incorporates a switched-capacitornetwork;

FIG. 2 shows details of the switched-capacitor network of the powerconverter shown in FIG. 1;

FIG. 3 shows the switch circuit of FIG. 2 configured for testing;

FIG. 4 shows the switched-capacitor network shown in FIG. 2 configuredto test leakage current across a first pair of switches;

FIG. 5 shows the switched-capacitor network shown in FIG. 2 configuredto test leakage current across a second pair of switches;

FIG. 6 shows the switched-capacitor network shown in FIG. 2 configuredto test leakage current across a third pair of switches;

FIG. 7 shows the switched-capacitor network shown in FIG. 2 configuredto measure RDSON of three of the six switches;

FIG. 8 shows the switched-capacitor network shown in FIG. 2 configuredto measure RDSON of the remaining three of the six switches;

FIG. 9 shows steps for testing leakage current; and

FIG. 10 shows steps for testing RDSON.

DETAILED DESCRIPTION

FIG. 1 shows a power converter 2 for receiving an input voltage VINprovided by a voltage source 3 and transforming it into an outputvoltage VOUT that is made available at an output capacitor 4 and a load5 thereof. The power converter 2 includes a controller 6 that controls aregulator 7 and a switched-capacitor network 8. As used herein, the terma “switched-capacitor network” includes a charge pump.

In the illustrated embodiment, the regulator 7 connects the voltagesource 3 to the switched-capacitor network 8. However, it is alsopossible for the regulator 7 to connect the switched-capacitor network 8to the output capacitor 4. The power converter 2 as shown can thereforebe viewed as a specific embodiment of a more general power converterthat comprises a first element connected to a second element, whereinwhen the first element is a regulator, the second element is aswitched-capacitor network and wherein when the first element is aswitched-capacitor network, the second element is a regulator.

In some cases, the regulator 7 is implemented as a switched inductorcircuit, examples of which include a buck converter, a boost converter,and a buck-boost converter. Such a switched-inductor circuit can beoperated with a duty cycle equal to zero, thus transforming it into amagnetic filter. As such, in some embodiments, the regulator 7 is simplya magnetic filter, such as an inductor.

In other cases, it is possible to obtain adequate performance with noregulator. Thus, embodiments of the power converter 2 also include thosewith just the switched-capacitor network 8.

Power converters of the type shown in FIG. 1 are described in detail inU.S. Pat. Nos. 8,860,396, 8,743,553, 8,723,491, 8,503,203, 8,693,224,8,724,353, 8,619,445, 9,203,299, 9,742,266, 9,041,459, U.S. PublicationNo. 2017/0085172, U.S. Pat. Nos. 9,887,622, 9,882,471, PCT PublicationNo. WO2017161368, PCT Publication No. WO2017/091696, PCT Publication No.WO2017/143044, PCT Publication No. WO2017/160821, PCT Publication No.WO2017/156532, PCT Publication No. WO2017/196826, and U.S. PublicationNo. 2017/0244318, the contents of which are all incorporated herein byreference.

FIG. 2 shows the switched-capacitor network 8 in more detail. Theswitched-capacitor network 8 includes a switching circuit 10 thatconnects to first, second, third, and fourth capacitors C1, C2, C3, C4.The switching circuit 10 is typically integrated onto a monolithicsubstrate and connected, via pins, to the capacitors C1-C4 that areeither on another monolithic substrate or that are provided as lumpedelements.

The switching circuit 10 includes power FETS that implement a firstswitch 12, a second switch 14, a third switch 16, a fourth switch 18, afifth switch 20, and a sixth switch 22. Each switch 12-22 has a currentpath that extends between its source and drain and a gate that opens andcloses the current path. In the illustrated embodiment, the third switch16 and the sixth switch 22 are implemented as PMOS transistors and theremaining switches are implemented as NMOS transistors.

The first and second switches 12, 14 connect at a first node N1A. Thesecond and third switches 14, 16 connect at a second node N2B. Thefourth switch 18 connects to the fifth switch 20 at a third node N2A.The fifth switch 20 connects to the sixth switch 22 at a fourth nodeN1B. Each of the nodes N1A, N1B, N2A, N2B connects to a correspondingone of the capacitors C1-C4.

The first, second, and third switches 12, 14, 16 together with the firstand second nodes N1A, N2B define a first charge-transfer path 24 thatextends between an input VX and an output node OUT_INT of theswitched-capacitor network 8. The fourth, fifth, and sixth switches 18,20, 22 and the third node N2A and the fourth node N1B define a secondcharge-transfer path 26 that likewise extends between the input VX andthe output node OUT_INT. A disconnect switch SD selectively connects anddisconnects the output node OUT_INT of the switching circuit 10 to anyother component. In FIG. 1, the component is an output capacitor 4.However, in the testing procedure discussed below, that component can bea voltage source or a voltmeter.

To control the first switch 12, it is necessary to control the amount ofcharge on its gate. Accordingly, the first switch's gate connects to afirst driver 28.

The first driver 28 functions as a switch that drives charge towards oraway from the first switch's gate. To control the first switch 12quickly, the amount of charge on its gate must change quickly. Thisrequires that the first driver 28 provide a large current into or out ofthe first switch's gate.

The first driver 28 switches between a first state and a second state.In the first state, the first driver 28 receives charge from a firstfloating-regulator 30 and provides it to the first switch's gate. In thesecond state, the first floating-regulator 30 removes charge from thefirst switch's gate and disposes of it via the first charge-transferpath 24.

During normal operation, the charge that the first floating-regulator 30ultimately provides to the first driver 28 when it is in the first statecomes from either the capacitor connected to the first node N1A or thecapacitor connected to the third node N2A. This is advantageous becauseit is not always possible to determine in advance which of these twocapacitors will be able to provide charge to meet thefloating-regulator's demand.

It is also possible to obtain charge from the voltage source 3 ratherthan from one of the two capacitors. This may occur during start-up ortesting.

Charge that comes from the capacitor connected to the first node N1Areaches a first regulator switch 32 through a first diode D1, the anodeof which connects to the first charge-transfer path 24. Charge that thecapacitor connected to the third node N2A reaches the first regulatorswitch 32 through a second diode D2, the anode of which connects to thesecond charge-transfer path 26. Charge that comes from the voltagesource 3 passes through the third diode D3, the anode of which connectsto the voltage source 3. The cathodes of the first, second, and thirddiodes D1, D2, D3 connect to the first regulator switch 32. Which ofthese three sources of charge is ultimately used depends on which of thethree anodes is at the highest voltage.

The first and second diodes D1, D2 provide cross-coupling between thefirst floating-regulator 30 and both the first and secondcharge-transfer paths 24, 26. The first regulator switch 32 regulatesthe flow of this charge into the first driver 28. Charge that ultimatelyreaches the first driver 28 during the first driver's first stateultimately passes through the first regulator switch 32.

As a result of the placement of the first and second diodes D1, D2, thefirst floating-regulator 30 ultimately receives charge during normaloperation from either the capacitor connected to the third node N2A orfrom the capacitor connected to the first node N1A. This is advantageoussince it is difficult to predict which of these capacitors will be ableto provide charge to supply the first floating-regulator's demand forcurrent.

In order to close the first switch 12, it is necessary to create aconducting path between its drain and source terminals. To do so, it isnecessary to deposit enough charge on its gate to raise its gate voltagepast its source voltage by an amount that is sufficient to form theconducting channel. Therefore, in addition to depositing charge quicklyonto the gate, the first driver 28 must also deposit the correct amountof charge. If the first driver 28 fails to deposit enough charge, theconducting channel will be too small and hence excessively resistive. Ifthe first driver 28 deposits too much charge, the first switch 12 can bedamaged.

The correct amount of charge is one that raises the gate's voltage pastthe source's voltage by a particular amount. A difficulty that arises isthat the source voltage floats. It is not fixed. This means that thecorrect gate voltage cannot be fixed. It must float with the source'svoltage.

The first floating-regulator 30 achieves this by having a referencepoint that is offset above the source's floating voltage. In theillustrated embodiment, a Zener diode 34 creates this reference point.

The Zener diode 34, a first resistor R1, and a second resistor R2together define a path that extends between the output node OUT_INT andthe first switch's source. The voltage drop along this path is thereforethe difference between the voltage at the output node OUT_INT and thefloating source voltage.

The anode of a fourth diode D6 connects to the voltage source 3. Itscathode connects to the node at which the first and second resistors R1,R2 also connect. This is useful to avoid a potential short-circuit withthe voltage source 3. The fourth diode D6 and the third diode D3cooperate during testing to provide power to operate the firstfloating-regulator 30.

The Zener diode's anode connects to the first switch's source and itscathode connects to the second resistor R2. As such, the voltage at theZener diode's cathode will always be a fixed offset above the firstswitch's source voltage. The remainder of the voltage drop, if any,between the source voltage and the output node OUT_INT is borne by thefirst and second resistors R1, R2.

The Zener diode 34 cannot itself carry significant current. However, itcan be placed in parallel with a path that can carry a significantcurrent. If this is done in such a way that the voltage drop across sucha path crudely tracks the Zener diode, a voltage with the correct offsetabove the floating source voltage can be generated.

The Zener diode 34, in effect, functions as a voltage source thatmaintains a voltage that exceeds the floating source voltage by somefixed offset, the value of which depends on the VI characteristic of theZener diode 34. This voltage, when made available to the gate of thefirst regulator switch 32, enables the first regulator switch 32 toprovide a voltage to the first driver 28, when it is switched into itsfirst state, suitable for forming a suitable conducting channel, thusclosing the first switch 12.

A significant feature of the first floating-regulator 30 is thefirst-regulator shunt TM3. During normal operation of theswitched-capacitor network 8, the switching circuit 10 connects to thecapacitors C1, C2, C3, C4 and is actively engaged in converting onevoltage into another. In this case, the first-regulator shunt TM3 isnon-conducting. As a result, the current that biases the first regulatorswitch 32 passes into the first charge-transfer path 24.

However, shortly after being manufactured at a semiconductor fabricationfacility, it is desirable to test the switching circuit 10. Inparticular, it is desirable confirm that the leakage currents and RDSONvalues for the various switches 12, 14, 16, 18, 20, 22 are within thedesign specifications. At some point during this testing, thefirst-regulator shunt TM3 will be made to conduct. As a result, thefirst-regulator shunt TM3 directs this same biasing current to groundinstead of to the first charge-transfer path 24. This prevents thebiasing current from mixing with whatever current is already on thefirst charge-transfer path 24. This also collapses the supply voltage tothe first driver 28.

This testing is expected to be the only time in the lifetime of theswitching circuit 10 that the first-regulator shunt TM3 will be made toconduct. The first-regulator shunt TM3 is therefore only used duringtesting.

The second switch 14 likewise has an associated second driver 36connected between a second floating-regulator 38 and the firstcharge-transfer path 24 at the first node N1A. The secondfloating-regulator 38 includes a second regulator switch 40 thatregulates the flow of this charge into the second driver 36 and a Zenerdiode 42 connected to maintain a relatively constant gate voltage acrossthe second driver 36.

The second floating-regulator 38 receives current from either the secondnode N2B or the fourth node N1B. Therefore, like the firstfloating-regulator 30, the second floating-regulator 38 is cross-coupledbetween the first and second charge-transfer paths 24, 26. The structureand operation of the second floating-regulator 38 is similar to thatalready discussed in connection with the first floating-regulator 30.

Like the first floating-regulator 30, the second floating-regulator 38features a second-regulator shunt TM2. During normal operation of theswitched-capacitor network 8, the second-regulator shunt TM2 remainsnon-conducting. As a result, current for biasing the second regulatorswitch 40 flows into the first charge-transfer path 24 and joinswhatever current is already there. At some time during testing, thesecond-regulator shunt TM2 will be made to conduct. This causes thiscurrent to pass to ground instead of to the first charge-transfer path24. Once testing is complete, the second-regulator shunt TM2 is expectedto never be used again.

The output node OUT_INT supplies current directly to a third driver 44for charging the third switch's gate. When the third driver 44 does notneed current, this current goes to a third floating-regulator 46.Additionally, when the third driver 44 removes current from the thirdswitch's gate, that current also goes to the third floating-regulator46.

In either case, the third floating-regulator 46 recycles the charge inthis current by passing it to either the second node N2B or to thefourth node N1B through which it ultimately reaches a capacitor C2, C4.Therefore, like the first floating-regulator 30, the thirdfloating-regulator 38 is cross-coupled between the first and secondcharge-transfer paths 24, 26.

The operation of the third floating-regulator 46 is slightly differentfrom that of the first and second regulators 30, 38 because the thirdswitch 16 is implemented as a PMOS transistor.

Like the first floating-regulator 30, the third floating-regulator 46includes a Zener diode 47 in series with a resistor R3. The Zener diodeagain functions as a voltage source that supplies a voltage equal to thethird switch's source voltage with a fixed offset. Since this Zenerdiode is in parallel with the third driver 44, this voltage ensuresplacement of the correct amount of charge on the third switch's gate toclose the switch.

Also, like the first floating-regulator 30, the third floating-regulator46 includes first and second diodes D4, D5. However, instead ofsupplying charge from capacitors, these diodes D4, D5 supply charge tocapacitors. The first diode D4 supplies charge to a capacitor connectedto the fourth node N1B and the second diode D5 supplies charge to acapacitor connected to the second node N2B. The charge in both casescomes from the third driver 44.

The third floating-regulator 46 features a third-regulator shunt TM1.During normal operation of the switched-capacitor network 8, thethird-regulator shunt TM1 remains non-conducting. As a result, currentthat enters the third floating-regulator 46 ultimately drains to eitherthe second node N2B or to the fourth node N1B and into one of the firstand second transfer-paths 24, 26. At some time during testing, thethird-regulator shunt TM1 will be made to conduct, thus shunting currentto ground instead of to one of the first and second charge-transferpaths 24, 26.

The switching circuit 10 also has drivers and regulators for theswitches in the second transfer path 26. These are mirror images of thecorresponding strictures along the first charge-transfer path 24.Accordingly, descriptions thereof are omitted to avoid prolixity.

After having manufactured the switching circuit 10, it is desirable totest one or more switches to confirm that those switches meet designspecifications for both leakage current and RDSON. FIGS. 9 and 10 showsmethods for doing so.

Part of manufacturing the switching circuit 10 is to test the leakagecurrent and RDSON of each switch 12, 14, 16, 18, 29, 22. This includesconnecting the switching circuit 10 to a test controller 48 as shown inFIG. 3.

Referring first to FIG. 4, to test the leakage current of the firstswitch 12, the test controller 48 opens the first switch 12.

As can be seen in FIG. 4, the first floating-regulator 30 receivescurrent from the output node OUT_INT. In normal operation, this currentwould exit the first floating-regulator 30 and return to a node of lowerpotential via the first charge-transfer path 24. However, because theleakage current will also be flowing through the first charge-transferpath 24, this extra current will pollute the measurement of leakagecurrent. To prevent pollution of the measurement by this extra current,the test controller 48 closes the first-regulator shunt TM3. Thisenables current leaving the first floating-regulator 30 to bypass thefirst charge-transfer path 24 on its way to a node of lower potential.As a result, the only current that will flow through the firstcharge-transfer path 24 will be the leakage current that is to bemeasured.

The test controller 48 connects a current meter 85 between a voltagesource and the first node N1A. The voltage source then applies a voltageat the drain of the first switch 12. Since the source of the firstswitch 12 is grounded by that test controller 48, a test voltagedevelops across the first switch's drain and source terminals. The testvoltage is selected based upon the voltage rating of the switch undertest.

In response to this applied voltage, a leakage current flows through theopened first switch 12. This leakage current draws current through thecurrent meter 85 towards the first node N1A. To the extent this currentall flows along the first charge-transfer path 24 toward the firstswitch 12, it is equal to the leakage current.

However, one cannot take it for granted that all current passing throughthe current meter 85 will be leakage current. It is apparent frominspecting the circuit's topology that when current reaches the firstnode N1A, it will have three choices on where to go next, only one ofwhich is in the direction of the first switch 12.

To obtain an accurate measurement, it is important that, upon reachingthe first node N1A, all of this current be directed toward the firstswitch 12. This is carried out by placing various impediments to currentflowing through any path but the desired path.

The most significant alternative path is through the second switch 14.Thus, the test controller 48 opens the second switch 14 to discouragecurrent entering the first node N1A from going through the second switch14.

However, this is not enough. The second switch 14 is a MOSFET.Therefore, has an inherent body diode. The orientation of this bodydiode's cathode and anode creates the possibility that current enteringthe first node N1A will flow through the body diode instead of throughthe first switch.

To suppress this possibility, the test controller 48 also applies avoltage at the drain of the second switch 14. This biases the body diodeand thus discourages entry of current that enters the first node N1A,thereby encouraging all current entering the first node N1A to passthrough the first switch 12. As a result, when the current meter 85reports its measurement, that measurement will indeed reflect theleakage current and not the sum of the leakage current and some othercurrent that ultimately went elsewhere.

As shown, the voltage applied at the second node N2B is 26 volts and thevoltage applied at the first node N1A is 20 volts, thus leading to asix-volt bias across the second switch 14. For those cases in which theswitches are implemented as MOSFETs, it would also be possible to apply20 volts at the second node N2B in which case the net applied voltageacross the second switch 14 would be zero. This would still suppresscurrent flow through the second switch 14 because would have anintrinsic body diode that would block current flow driven until thevoltage driving that current flow increases beyond the potential barrierimposed by that body diode's space-charge layer.

The remaining alternative path is one that leads to the firstfloating-regulator 30 and a fourth floating-regulator connected to thefourth switch 18. However, it is apparent from inspection of thetopology that this path will already be blocked because the firstregulator switch 32 and a regulator switch in the fourthfloating-regulator will have been opened.

FIG. 4 also shows the test controller 48 testing the leakage current ofthe fourth switch 18 at the same time. Such testing is carried out usingthe same methods used in connection with testing the leakage current ofthe first switch 12.

FIG. 5 shows the test controller 48 concurrently testing the leakagecurrents at the second switch 14 and at the fifth switch 20. The sameprinciples discussed in connection with the leakage current measurementof the first and fourth switches 12, 18 in FIG. 4 are used in themeasurement shown in FIG. 5.

In FIG. 5, the test controller 48 closes the second-regulator shunt TM2for the same reason it closed the first-regulator shunt TM3. The testcontroller 48 applies 40 volts to the drain voltage of the disconnectswitch SD and 36 volts to the drain of the second switch 14. As aresult, the net voltage across the source and drain terminals of thethird switch 16 is four volts minus the body diode drop of thedisconnect switch SD. This nevertheless discourages current flow throughthe body diode of the third switch 16 because the body diode's ownspace-charge layer will create a potential barrier to suppress suchcurrent flow.

FIG. 6 shows the test controller 48 concurrently testing the leakagecurrents at the third switch 16 and at the sixth switch 22. The sameprinciples discussed in connection with the leakage current measurementof the first and fourth switches 12, 18 in FIG. 4 are used in themeasurement shown in FIG. 6.

In addition to measuring leakage current, the test controller 48 alsomeasures RDSON for each switch 12-22.

Closing a switch 12-22 forms a conducting channel between the source anddrain. It is through this channel that charge flows. However, thischannel, being made from a semiconductor, has a non-negligibleresistance. This resistance is RDSON. If RDSON is too high, energy willbe lost through heating. As a result, it is important to confirm thatthe RDSON value is consistent with design specifications.

A useful way to measure RDSON is apply a suitable gate voltage so as tocreate the conducting channel, to inject a known current through thischannel, and to then measure the voltage between the source terminal andthe drain terminal. The ratio of this voltage measurement and the knowncurrent provides a way to determine RDSON.

This method is particularly useful for the circuit shown in FIG. 2because each charge-transfer path 24, 26 passes through the conductingchannels of three switches 12-16, 18-22. This makes it possible toinject one known current into the charge-transfer path 24, 26 and tothen concurrently measure the voltages across three switches 12-16,18-22.

FIG. 7 shows the test controller 48 making an RDSON measurement for theswitches 12-16 on the first charge-transfer path 24.

The test controller 48 closes all the switches 12-16 on the firstcharge-transfer path 24 and opens all the switches 18-22 on the secondcharge-transfer path 26. This ensures that the known current flowsthrough only the first charge-transfer path 24. A bias voltage source VTconnected to the output causes the source voltages of all the switches12-16 on the first charge-transfer path 24 to be close a bias voltageVT. Because of this bias voltage, the voltage provided to the first andsecond regulators 30, 38 to provide power to their respective gatedrivers 28, 36 is the bias voltage VT increased by the gate voltage VGrequired to close the relevant switch 12, 14, 16.

The test controller 48 then connects first, second, and third voltmeters90, 92, 94 across the drain and source terminals of the first, second,and third switches 12, 14, 16 respectively.

The test controller 48 then connects a test current source IT so as toforce a known current through the first charge-transfer path 24. As aresult of this current, the bias voltage VT measured by the firstvoltmeter 90 will drop by a small amount VΔ4−VΔ3 as a result of theRDSON of the first switch 12. The second and third voltmeters 92, 94will likewise measure small drops VΔ3−VΔ2 and VΔ2−VΔ1 caused by theRDSON values of the second and third switches 14, 16.

It is important that the current that actually flows through the firstcharge-transfer path 24 in fact be equal to the current provided by thecurrent source IT. This means that no current should enter or leave thefirst charge-transfer path 24.

When measuring leakage current, the most significant source ofinaccuracy arose from current that was being used to bias thefloating-regulators. These currents would eventually find their way intofirst charge-transfer path 24. Once there, these currents would add tothe leakage current that was already there. Since the leakage currentwas small, even this stray current was enough to taint the measurementsof leakage current.

When measuring RDSON, the known current provided by the test currentsource IT is quite large. As such, the entry of stray currents used tobias the floating-regulators matters less. However, it is still possiblefor some of this test current to either stray away from the firstcharge-transfer path 24 or to fail to enter the first charge-transferpath 24 in the first place. In either case, the result is a poorerestimate of RDSON.

To ensure that all the test current at least enters the firstcharge-transfer path 24, it is useful to open all the switches that areon the second charge-transfer path 26, namely the fourth switch 18, thefifth switch 20, and the sixth switch 22.

Once the test current is on the first charge-transfer path 24, it isstill possible for it to prematurely leave the path by entering one ofthe first and second floating-regulators 30, 38. To avoid this, it isuseful to reverse bias the first and second diodes D1, D2 of each of thefirst and second floating-regulators 30, 38.

The process of reverse biasing includes applying, to the anode of thethird diode D3 of each of the first and second floating-regulators 30,38, a voltage that is in excess of the bias voltage VT. In theillustrated example, this excess over the bias voltage VT is selected tobe the gate voltage VG. As a result, the applied gate voltage VG isdoing two things at once: it is biasing a switch and also confining testcurrent in the first charge-transfer path 24 by suitably biasing thefirst and second diodes D1, D2, thereby barring the entry of any testcurrent into the first and second floating-regulators 30, 38.

FIG. 8 shows the test controller 48 configured to measure RDSON for theswitches 18, 20, 22 on the second charge-transfer path 26. Theconfiguration is essentially the mirror image of that described inconnection with the switches 12, 14, 16 on the first charge-transferpath 24.

In some cases, it is also useful to measure RDSON of the disconnectswitch SD as well as the switches within the switching circuit 10. Thetest controller 48 carries this out by connecting a fourth voltmeter 96between a testing pin 98 and the output of the switched-capacitornetwork 8 and then closing a testing switch 100 that couples the testingpin 98 to the output node OUT_INT of the switching circuit 10. Thistesting switch 100 remains open during normal operation and is onlyclosed for this testing procedure. Closing the testing switch 100 placesthe fourth voltmeter's terminals on the drain and source of thedisconnect switch SD.

The test controller 48 implements a method for testing switches.

The method described and claimed herein results in an improvement to atechnological field, namely the field of testing semiconductor devices.To the extent the set of all such methods can be divided into abstractmethods and non-abstract methods, the methods as described herein areonly the non-abstract methods. Any descriptions of abstract methods havebeen specifically excluded from this specification. In addition, themethods described herein are only those that cannot be carried out by ahuman being using only a writing implement and paper. Thus, none of themethods described and claimed herein are purely mental steps.

FIG. 9 shows a non-abstract testing method 50 for estimating the leakagecurrent through a switch 12.

The process begins by opening the switch 12 whose leakage current is tobe estimated (step 52) and applying a known voltage across it. Inresponse to this voltage, a small leakage current will flow through theswitch 12 (step 54).

However, the process of controlling switches 12 itself requires current.These currents pass through the various floating-regulators and driversthat control the switches. Collectively, these currents will be referredto herein as “biasing current” to distinguish them from the “leakagecurrent” that is of interest. In normal operation, these biasingcurrents ultimately make their way to the same path that goes throughthe switch 12.

Given the relative magnitudes of the biasing current and the leakagecurrent that is to be measured, it is important that this current not beallowed to mix with the leakage current. Otherwise, the estimate ofleakage current will be degraded.

To maintain the purity of the leakage current, the method includes thestep of diverting the biasing current so that it does not mix with theleakage current that is to be measured (step 56). Typically, the biasingcurrent is simply diverted to ground. One way to do so is to closecorresponding shunts TM1, TM2, TM3. In either case, a result of thisdiversion, the biasing current will not mix with the leakage current.

The process then continues with measuring the current through the switch(step 58). One way to do this is to place a current sensor along thatcurrent path to sense the amount of this leakage current.

Because the current through the switch is now uncontaminated by currentfrom any other source, it provides a basis for estimating the leakagecurrent (step 60). The method then proceeds with determining whether theestimate of leakage current is within a design specification (step 62).If it is not, then the switching network is rejected (step 64).Otherwise, the process determines if there are more switches to test(step 66) and if so, proceeds to test the next switch (step 52).Otherwise, the circuit is passed (step 68).

FIG. 10 shows a process 70 for estimating the RDSON of several switches12, 14, 16 at the same time.

This process begins by closing the switches 12, 14, 16 that are to betested (step 72) and causing a known test current to enter a firstcharge-transfer path 24 that passes through all of the switches 12, 14,16 (step 74). The process also includes taking steps to prevent thattest current from escaping the first charge-transfer path 24 until ithas passed through every switch 12, 14, 16 (step 76).

The testing current that enters the first charge-transfer path 24 isprone to escaping by passing through floating-regulators that are usedto drive the switches. One way to suppress such escape is to prevententry of any portion of the testing current into a floating-regulator.This can be carried out by applying a voltage that reverse biases adiode that would otherwise admit current into the floating-regulator.This applied voltage that biases this diode can also be used inconnection with driving the switch.

The voltages across the switches 12, 14, 16 can then be measured at thesame time or at essentially the same time (step 78). Based on thesemeasured voltages and the known current, it is possible to estimate theRDSON of each switch 12, 14, 16 (step 80). This is typically carried outby dividing the measured voltage by the known value of current. Thequotient that results from dividing this measured voltage by the knowncurrent is an estimate of RDSON.

The process proceeds with comparing the voltages to a designspecification (step 82). If any voltage is outside the designspecification, the circuit is rejected (step 84). If not, the processdetermines if any more switches are to be tested. If there are none, thecircuit is marked as having completed the RDSON test (step 86).Otherwise, the process continues with testing the next switches.

As used herein, a “controller” refers to a tangible piece of hardwarethat consumes electrical energy in the course of performing work thatincludes moving electrical charge. The controller is made of acombination of baryonic matter and leptons. The controller generateswaste heat and thus warms its environment. The controller has mass andis not an intangible structure. Nor is the controller software per se.

In some implementations, a tangible and non-transitory computer-readablestorage-medium includes a database representative of one or morecomponents of the power converter 2. Among these are implementations inwhich the database includes data representative of a switching circuit10 that has been optimized to promote low-loss operation of theswitched-capacitor network 8.

As used herein, a computer-readable storage-medium includes anynon-transitory storage media accessible by a computer during use toprovide instructions and/or data to the computer. Examples ofcomputer-readable storage-media include storage media such as magneticdisks, optical disks, and semiconductor memories. These are non-abstractstructures that are made of matter having interacting baryons andleptons.

In particular embodiments, a database representative of the system is adatabase or other data structure that is readable by a program and used,directly or indirectly, to fabricate the hardware comprising the system.The database is manifested in the real world by rearrangements ofcertain attributes of matter such as charge and direction of spin.

One example of such a database is a behavioral-level description orregister-transfer level (RTL) description of the hardware functionalityin a high-level design language (HDL) such as Verilog or VHDL. Thedescription may be read by a synthesis tool that may synthesize thedescription to produce a netlist comprising a list of gates from asynthesis library. The netlist comprises a set of gates that alsorepresent the functionality of the hardware comprising the system. Thenetlist may then be placed and routed to produce a data set describinggeometric shapes to be applied to masks. The masks may then be used invarious semiconductor fabrication steps to produce a semiconductorcircuit or circuits corresponding to the system. In other examples,alternatively, the database may itself be the netlist, with or withoutthe synthesis library, or the data set.

Various features, aspects, and embodiments of switched-capacitorpower-converters have been described herein. The features, aspects, andnumerous embodiments described are susceptible to combination with oneanother as well as to variation and modification, as will be understoodby those having ordinary skill in the art. The present disclosureshould, therefore, be considered to encompass such combinations,variations, and modifications.

Additionally, the terms and expressions that have been employed hereinare used as terms of description and not of limitation. There is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described, or portions thereof. Itis recognized that various modifications are possible within the scopeof the claims. Other modifications, variations, and alternatives arealso possible. Accordingly, the claims are intended to cover all suchequivalents.

Having described the invention and embodiments thereof, what is claimed as new and secured by Letters Patent is:
 1. An apparatus comprising a switching network, wherein the switching network, while connected to a plurality of capacitors, forms a switched-capacitor network, the switched-capacitor network is to transform a first voltage into a second voltage, wherein the switching network comprises a switch, a driver, and a floating-regulator, wherein the switch connects to a floating voltage, wherein the driver is configured to drive the switch using a drive voltage, wherein the floating-regulator is configured to rely on a voltage provided by an external voltage source for causing the drive voltage to be at a fixed offset from the floating voltage, and wherein the external voltage source is external to the switched-capacitor network, wherein the floating-regulator comprises a first terminal and a first output, wherein the first terminal is maintained at a voltage that depends on the floating voltage, and wherein the first output is maintained at a voltage that depends on the fixed offset, wherein the driver is connected between the first terminal and the first output.
 2. The apparatus of claim 1, wherein the floating-regulator comprises a first path that connects a voltage provided by the external voltage source to the driver and a second path that connects a voltage corresponding to the fixed offset to the driver.
 3. The apparatus of claim 1, wherein the floating-regulator comprises a regulator switch disposed along a first path, the first path connecting a voltage provided by a voltage source that is external voltage to the driver via and a Zener diode disposed along a second path, the second path connecting a voltage corresponding to the fixed offset to the driver.
 4. The apparatus of claim 1, further comprising a controller configured to cause a bias current to hold the switch in a conducting state, to divert the bias current so that the bias current avoids interfering with a known current that is injected through the switch, to cause injection of the known current through the switch, to measure a voltage across the switch, and to estimate an RDSON of the switch conducts based on the measurement of the voltage and the known current.
 5. The apparatus of claim 1, wherein the switch is one of a first plurality of switches that are arranged in series to define a first charge-transfer path that extends from an input of the switching network to an output of the switching network, wherein the first charge-transfer path comprises nodes at which switches from the first plurality of switches connect, and wherein the nodes are configured to be connected to the plurality of capacitors.
 6. A method comprising: estimating an RDSON value for a switch that, along with a driver that drives the switch and a floating-regulator for controlling the driver, is a constituent of a switching network that while connected to a plurality of capacitors, forms a switched-capacitor network, the switched-capacitor network is formed for transforming a first voltage into a second voltage, wherein the switch is disposed along a charge-transfer path, wherein the switch connects to a floating voltage, wherein estimating RDSON values comprises causing a known current to flow through the charge-transfer path and estimating an RDSON value for the switch; wherein the floating-regulator comprises a first terminal and a first output, wherein the first terminal is maintained at a voltage that depends on the floating voltage, and wherein the first output is maintained at a voltage that depends on a fixed offset from the floating voltage, wherein the driver is connected between the first terminal and the first output.
 7. The method of claim 6, wherein the switch is one of a plurality of switches in series along the charge-transfer path and the method comprises concurrently obtaining voltage measurements across each of the switches and estimating the RDSON values based on the voltage measurements.
 8. The method of claim 6, wherein causing a known current to flow through the charge-transfer path comprises inhibiting opportunities for the current to stray from the charge-transfer path.
 9. An apparatus comprising a switching network, wherein the switching network, while connected to a plurality of capacitors, forms a switched-capacitor network, the switched-capacitor network is to transform a first voltage into a second voltage, wherein the switching network comprises a switch, a driver, and a floating-regulator, wherein the switch connects to a floating voltage, wherein the driver is configured to drive the switch using a drive voltage, wherein the floating-regulator is configured to rely on a voltage provided by an external voltage source for causing the drive voltage to be at a fixed offset from the floating voltage, and wherein the external voltage source is external to the switched-capacitor network, wherein the floating-regulator comprises a regulator switch disposed along a first path, the first path connecting a voltage provided by a voltage source that is external voltage to the driver via and a Zener diode disposed along a second path, the second path connecting a voltage corresponding to the fixed offset to the driver.
 10. An apparatus comprising a switching network and a controller, wherein the switching network, while connected to a plurality of capacitors, forms a switched-capacitor network, the switched-capacitor network is to transform a first voltage into a second voltage, wherein the switching network comprises a switch, a driver, and a floating-regulator, wherein the switch connects to a floating voltage, wherein the driver is configured to drive the switch using a drive voltage, wherein the floating-regulator is configured to rely on a voltage provided by an external voltage source for causing the drive voltage to be at a fixed offset from the floating voltage, and wherein the external voltage source is external to the switched-capacitor network, wherein the controller is configured to cause a bias current to hold the switch in a conducting state, to divert the bias current so that the bias current avoids interfering with a known current that is injected through the switch, to cause injection of the known current through the switch, to measure a voltage across the switch, and to estimate an RDSON of the switch conducts based on the measurement of the voltage and the known current. 